1. Field of Invention
This invention relates to a chair frame for stackable chairs. More specifically, the present invention is related to a chair frame provided with a bracing system that enhances the durability of the resulting chair without impairing the ease with which chairs utilizing the frame can be stacked, or the stability of the resulting stack of chairs.
2. Description of the Related Art
Chairs which can be stacked upon one another to facilitate their storage are known in the art. For example, such chairs are disclosed in U.S. Pat. Nos. 3,316,016, 4,057,288, 5,762,396, and 6,174,029 B1. It is desirable that stackable chairs be light weight, such that they can be easily lifted during stacking and unstacking. Therefore, stackable chairs are typically fabricated of light weight tubular metal materials, such as aluminum. However, stackable chairs tend to take a great deal of abuse, particularly while being stacked or unstacked, and such light weight fabricating materials can deform, or otherwise be damaged, such that a chair may not stack properly or be useable for seating. For example, maintenance of the desired angular disposition of the back of a stackable chair relative to the seat portion may be critical to the proper stacking of chairs. Where the back support portion of the chair frame has been bent or deformed, the chair may not properly interlock with the chair stacked above, making stacking impossible, or rendering the resulting stack of chairs unstable. With chairs which are not stackable, bracing structures can easily be added without great concern over the additional weight. However, locating bracing structures on stackable chairs without impairing the ability of the chairs to properly and efficiently interlock for purposes of stacking can be problematic. Moreover, adding extensive bracing structures to the primary components of a stackable chair increases the weight of the chair, such that the ease with which the chairs can be stacked and unstacked can be compromised.
In U.S. Pat. No. 3,203,731 a stackable chair having a folding back is disclosed. Because the back portions are folded down over the seat prior to stacking, the need for reinforcing the connection between the back portion and seat portion to insure stackability is obviated, but the hinge mechanism which is required adds cost to the chair. In addition, the relatively thick back portion is folded over the seat portion, fewer chairs can be stacked without the height of the stack becoming untenable. Accordingly, the prior art does not disclose a chair frame which adequately addresses the problem of deformation of, or damage to, the chair frame which undermines the stackability of stackable chairs.